Fin Field Effect Transistor (FINFET) Device with Controlled End-to-End Critical Dimension and Method for Forming the Same

ABSTRACT

A method for forming a fin field effect transistor (FinFET) device structure is provided. The FinFET device structure includes a substrate and a first fin structure and a second fin structure extending above the substrate. The FinFET device structure also includes a first transistor formed on the first fin structure and a second transistor formed on the second fin structure. The FinFET device structure further includes an inter-layer dielectric (ILD) structure formed in an end-to-end gap between the first transistor and the second transistor, and the end-to-end gap has a width in a range from about 20 nm to about 40 nm.

PRIORITY CLAIM AND CROSS-REFERENCE

This application is a continuation of U.S. patent application Ser. No. 15/362,603 filed on Nov. 28, 2016 and entitled “Fin Field Effect Transistor (FinFET) Device with Controlled End-To-End Critical Dimension and Method for Forming the Same,” which is a continuation of U.S. patent application Ser. No. 14/554,682, filed on Nov. 26, 2014 and entitled “Fin Field Effect Transistor (FinFET) Device with Controlled End-To-End Critical Dimension and Method for Forming the Same,” now U.S. Pat. No. 9,508,719 issued on Nov. 29, 2016, which applications are incorporated herein by reference.

BACKGROUND

Semiconductor devices are used in a variety of electronic applications, such as personal computers, cell phones, digital cameras, and other electronic equipment. Semiconductor devices are typically fabricated by sequentially depositing insulating or dielectric layers, conductive layers, and semiconductive layers of material over a semiconductor substrate, and patterning the various material layers using lithography to form circuit components and elements thereon. Many integrated circuits are typically manufactured on a single semiconductor wafer, and individual dies on the wafer are singulated by sawing between the integrated circuits along a scribe line.

As the semiconductor industry has progressed into nanometer technology process nodes in pursuit of higher device density, higher performance, and lower costs, challenges from both fabrication and design issues have resulted in the development of three-dimensional designs, such as the fin field effect transistor (FinFET). FinFETs are fabricated with a thin vertical “fin” (or fin structure) extending from a substrate. The channel of the FinFET is formed in this vertical fin. A gate is provided over the fin. Advantages of the FinFET may include reducing the short channel effect and higher current flow.

Although existing FinFET devices and methods of fabricating FinFET devices have been generally adequate for their intended purpose, they have not been entirely satisfactory in all aspects.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It should be noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

FIG. 1 shows a perspective representation of a fin field effect transistor (FinFET) device structure, in accordance with some embodiments of the disclosure.

FIG. 2 shows a top-view of a fin field effect transistor (FinFET) device structure, in accordance with some embodiments of the disclosure.

FIGS. 3A-3I show cross-sectional representations of various stages of forming a fin field effect transistor (FinFET) device structure, in accordance with some embodiments of the disclosure.

FIGS. 4A-4G show cross-sectional representations of various stages of forming a fin field effect transistor (FinFET) device structure, in accordance with some embodiments of the disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, or examples, for implementing different features of the subject matter provided. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

Some variations of the embodiments are described. Throughout the various views and illustrative embodiments, like reference numbers are used to designate like elements. It should be understood that additional operations can be provided before, during, and after the method, and some of the operations described can be replaced or eliminated for other embodiments of the method.

Embodiments for forming a fin field effect transistor (FinFET) device structure are provided. FIG. 1A shows a perspective representation of a fin field effect transistor (FinFET) device structure 100, in accordance with some embodiments of the disclosure.

The FinFET device structure 100 includes a substrate 102. The substrate 102 may be made of silicon or other semiconductor materials. Alternatively or additionally, the substrate 102 may include other elementary semiconductor materials such as germanium. In some embodiments, the substrate 102 is made of a compound semiconductor such as silicon carbide, gallium arsenic, indium arsenide, or indium phosphide. In some embodiments, the substrate 102 is made of an alloy semiconductor such as silicon germanium, silicon germanium carbide, gallium arsenic phosphide, or gallium indium phosphide. In some embodiments, the substrate 102 includes an epitaxial layer. For example, the substrate 102 has an epitaxial layer overlying a bulk semiconductor.

FinFET device structure 100 also includes one or more fin structures 104 (e.g., Si fins) that extend from the substrate 102. Fin structures 104 may optionally include germanium. The fin structures 104 may be formed by using suitable processes such as photolithography and etching processes. In some embodiments, the fin structures 104 are etched from the substrate 102 using dry etch or plasma processes.

An isolation structure 108, such as a shallow trench isolation (STI) structure, is formed to surround fin structures 104. In some embodiments, a lower portion of the fin structures 104 is surrounded by the isolation structure 108, and an upper portion of the fin structures 104 protrudes from the isolation structure 108, as shown in FIG. 1. In other words, a portion of the fin structures 104 is embedded in the isolation structure 108. The isolation structure 108 prevents electrical interference or crosstalk.

The FinFET device structure 100 further includes a gate stack structure including a gate electrode 110 and a gate dielectric layer 106. The gate stack structure is formed over a central portion of the fin structures 104. In some embodiments, multiple gate stack structures are formed over the fin structures 104. Numerous other layers may also be present in the gate structures, for example, capping layers, interface layers, spacer elements, and/or other suitable features.

The gate dielectric layer 106 may include dielectric materials, such as silicon oxide, silicon nitride, silicon oxynitride, dielectric material(s) with high dielectric constant (high-k), or combinations thereof. Examples of high-k dielectric materials include hafnium oxide, zirconium oxide, aluminum oxide, hafnium dioxide-alumina alloy, hafnium silicon oxide, hafnium silicon oxynitride, hafnium tantalum oxide, hafnium titanium oxide, hafnium zirconium oxide, the like, or combinations thereof. The gate electrode 110 may include polysilicon or metal. Metal includes tantalum nitride (TaN), nickel silicon (NiSi), cobalt silicon (CoSi), molybdenum (Mo), copper (Cu), tungsten (W), alumina (Al), cobalt (Co), zirconium (Zr), platinum (Pt), or other applicable materials.

The gate electrode 110 may be formed in a gate last process (or gate replacement process). In some embodiments, the gate stack structure includes additional layers, such as interfacial layers, capping layers, diffusion/barrier layers, or other applicable layers.

The fin structures 104 includes a channel region 114 surrounded or wrapped by the gate electrode 110 and the gate dielectric layer 106. The fin structures 104 may be doped to provide a suitable channel for an n-type FinFET (NMOS device) or a p-type FinFET (PMOS device). The fin structures 104 may be doped using a suitable process, such as an ion implantation process, diffusion process, annealing process, other applicable processes, or combinations thereof. The fin structures 104 include a source region 112 and a drain region 116, and the channel region 114 is between the source region 112 and the drain region 116. The FinFET device 100 may be a device included in a microprocessor, memory cell (e.g., Static Random-Access Memory (SRAM)), and/or other integrated circuits.

FIG. 2 shows a top-view of a fin field effect transistor (FinFET) device structure 100, in accordance with some embodiments of the disclosure. The FinFET device structure 100 includes multiple fin structures 104 and multiple gate electrodes 110. The gate electrodes 110 traverse over the fin structures 104. The FinFET device structure 100 is surrounded by the isolation structure 108.

As shown in FIG. 2, the fin structures 104 may be substantially parallel to each other. The gate electrodes 110 may also be parallel to each other and substantially perpendicular to the fin structures 104. In some embodiments, the gate electrodes 110 are also called gate electrode lines when seen from a top-view.

A first transistor 300 a is formed on the first fin structure 104 a, and a second transistor 300 b is formed on the second fin structures 104 b. In some embodiments, a third width (W₃) between first transistor 300 a and second transistor 300 b is in a range from about 10 nm to about 50 nm.

FIGS. 3A-3H show cross-sectional representations of various stages of forming a fin field effect transistor (FinFET) device structure 100, in accordance with some embodiments of the disclosure. FIGS. 3A-3H are cross-sectional representations taken along line AA′ of FIG. 2.

Referring to FIG. 3A, a first fin structure 104 a and a second fin structure 104 b are formed over the substrate 102. In some embodiments, the substrate 102 is etched to form the first fin structure 104 a and the second fin structure 104 b by depositing and patterning a hard mask layer (not shown) on the substrate 102. The hard mask layer forms a pattern covering a portion of the substrate 102. Afterwards, the substrate 102 is etched to form trenches between the regions covered by the hard mask layer. As a result, the first fin structures 104 and the second fin structure 104 b are formed between the trenches.

Afterwards, a dielectric material (e.g., silicon oxide) is deposited into the trenches, covering the first fin structure 104 a and the second fin structure 104 b. The dielectric material is planarized down to the top surfaces of the first fin structure 104 a and the second fin structure 104 b or the hard mask layer, and then the dielectric material is etched to a level below the top surfaces of the first fin structure 104 a and the second fin structure 104 b. As a result, an upper portion of the first fin structures 104 a and the second fin structure 104 b protrudes above the isolation structure 108, and a lower portion of the first fin structure 104 a and the second fin structure 104 b is surrounded and covered by the isolation structure 108.

Alternatively, in some other embodiments, the isolation structure 108 is formed over the substrate 102 first. Trenches between the isolation structure 108 are formed to expose the substrate 102. A semiconductor material, such as silicon, silicon germanium, or other applicable materials, is then grown in the trenches to form the first fin structure 104 a and the second fin structure 104 b by using, for example, an epitaxial process. After the first fin structure 104 a and the second fin structure 104 b are grown to the desired height, the isolation structure 108 is etched down to a level below the top surface of the first fin structure 104 a and the second fin structure 104 b. As a result, a portion of the first fin structure 104 a and the second fin structure 104 b protrudes above the isolation structure 108.

As shown in FIG. 3A, a dielectric layer 302 and a polysilicon layer 304 are formed sequentially on the first fin structure 104 a, the second fin structure 104 b and isolation structure 108. Afterwards, a first hard mask layer 306 a and a second hard mask layer 306 b are formed over the polysilicon layer 304. The first hard mask 306 a may be made of silicon oxide, silicon nitride, silicon oxynitride, or other applicable materials. The second hard mask 306 b may be made of silicon oxide, silicon nitride, silicon oxynitride, or other applicable materials. The first hard mask layer 306 a and the second hard mask layer 306 b are formed by a patterning process. The patterning process includes a photolithography process and an etching process. Photolithography processes include photoresist coating (e.g., spin-on coating), soft baking, mask aligning, exposure, post-exposure baking, developing the photoresist, rinsing and drying (e.g., hard baking). The etching process includes a dry etching process or a wet etching process.

After the first hard mask layer 306 a and the second hard mask layer 306 b are formed, a first photoresist layer 308 a and a second photoresist layer 308 b are formed on the second hard mask layer 306 b as shown in FIG. 3B, in accordance with some embodiments of the disclosure.

In some embodiments, the first photoresist layer 308 a is a carbon-rich layer, such as silicon carbide (SiC or Si_(x)C). In some embodiments, the second photoresist layer 308 b is a silicon-rich layer, such as silicon oxide (SiO_(x)), silicon nitride (Si_(x)N_(y)) or silicon oxynitride (SiON).

Afterwards, the first photoresist layer 308 a and the second photoresist layer 308 b are patterned to form a trench 350 in the first photoresist layer 308 a and the second photoresist layer 308 b. The trench has a first width W₁. In some embodiments, the first width W₁ is in a range from about 40 nm to about 80 nm.

After the trench 350 is formed, a coating layer 310 is conformally formed in the trench 350 and on the second photoresist layer 308 b as shown in FIG. 3C, in accordance with some embodiments of the disclosure. The coating layer 310 is a fluorine-containing polymer. The coating layer 310 is configured to reduce the width of the trench 350. After forming the coating layer 310, the trench 350 has a reduced second width W₂. Therefore, the second width W₂ is smaller than the first width W₁.

The coating layer 310 is formed by a coating process with a coating gas. In some embodiments, the coating process is a plasma process. The coating gas includes fluorine-containing gas, such as tetrafluoromethane (CF₄), difluoromethane (CH₂F₂), sulfur hexafluoride (SF₆), or nitrogen trifluoride (NF₃), another applicable gas or combinations thereof. The flow rate of the coating gas is in a range from about 0.1 sccm to about 100 sccm. A bias voltage used in plasma process is in a range from OV. A power used in the plasma process is in a range from about 500 Watt to about 1500 Watt.

The coating thickness of the coating layer 310 is dependent on the coating time. The coating time is in a range from about 1 second to about 50 seconds. If the coating time is too long, the trench 350 may be completely filled with the coating layer 310, and therefore the underlying layers cannot be patterned using the pattern of the trench 350. If the coating time is too short, the coating layer 310 is too thin to reduce the dimension of the trench 350.

It should be noted that, in order to prevent some unwanted residues (coming from the photoresist layer 308 a or 308 b) from remaining in the trench 350, a pre-cleaning process is performed on the trench 350 before the coating layer 310 is formed. When the trench 350 is cleaned, a line-end bridge problem that can be caused by the residues formed in the trench 350 is avoided.

The pre-cleaning process is performed by using a fluorine-containing gas. The fluorine-containing gas includes tetrafluoromethane (CF₄), sulfur hexafluoride (SF₆), or nitrogen trifluoride (NF₃), other applicable gas or combinations thereof. In some embodiments, the pre-cleaning process is performed for a period of time in a range from about 1 s to about 20 s.

After the coating layer 310 is formed in the trench 350, a first etching process 11 is performed to remove a portion of the coating layer 310 on the second photoresist layer 308 b as shown in FIG. 3D, in accordance with some embodiments of the disclosure. In some embodiments, the first etching process 11 is a dry etching process.

It should be noted that the portion of the coating layer 310 on the second photoresist layer 308 b is removed, but a portion of the coating layer 310 formed on the sidewall and bottom of the trench 350 remain. The remaining coating layer 310 is used to narrow the width of the trench 350. The top portion of the remaining coating layer 310 on the sidewalls of the trench 350 is slightly etched. Therefore, the top surface of the coating layer 310 is not parallel to the top surface of the second photoresist layer 308 b.

Afterwards, a second etching process 13 is performed to remove a portion of the coating layer 310 and the second photoresist layer 308 b as shown in FIG. 3E, in accordance with some embodiments of the disclosure. In some embodiments, the second etching process 13 is also a dry etching process.

After the second etching process 13, a third etching process 15 is performed to remove the coating layer 310, the first photoresist layer 308 a, a portion of the first hard mask layer 306 a and a portion of the second hard mask layer 306 b as shown in FIG. 3F, in accordance with some embodiments of the disclosure. In some embodiments, the third etching process 15 is a dry etching process.

It should be noted that the bottom of the trench 350 is selectively etched by the third etching process 15. In addition, the portion of the second hard mask layer 306 b directly under the coating layer 310 is etched afterwards to expose the portion of the first hard mask layer 306 a. Afterwards, the exposed first hard mask layer 306 a is removed. The first hard mask layer 306 a is an etching stop layer.

As a result, as shown in FIG. 3F, the first hard mask layer 306 a and the second hard mask layer 306 b are patterned to form a trench 352. The trench 352 has a third width W₃. The third width W₃ is slightly larger than the second width W₂, and the third width W₃ is still smaller than the first width W₁. In some embodiments, the third width W₃ is in a range from about 10 nm to about 50 nm.

After the trench 352 is formed, the dielectric layer 302 and the polysilicon layer 304 are patterned by using the first hard mask layer 306 a and the second hard mask layer 306 b as a mask as shown in FIG. 3G, in accordance with some embodiments of the disclosure. As a result, a trench 354 is formed in the polysilicon layer 304. In other words, the trench 354 is called as an end-to-end gap.

Afterwards, the first hard mask layer 306 a and the second hard mask layer 306 b are removed, and a dielectric material is filled into the trench 354 (or called end-to-end gap) and on the polysilicon layer 304 as a mask as shown in FIG. 3H, in accordance with some embodiments of the disclosure.

After dielectric material is filled, a portion of dielectric material out of trench 354 is removed by a planarizing process, such as a chemical mechanical polishing process (CMP). As a result, an inter-layer dielectric (ILD) structure 320 is formed.

Afterwards, the polysilicon layer 304 and the dielectric layer 302 are removed, and the gate dielectric layer 106 and the gate electrode 110 are formed on the fin structure 104 as shown in FIG. 3I, in accordance with some embodiments of the disclosure. In some embodiments, the gate dielectric layer 106 is a high dielectric constant (high-k) dielectric layer, and the gate electrode 110 is metal gate electrode. In other words, a HK/MG stack structure is formed on the fin structure 104.

The metal gate electrode includes n-type work function metal or p-type work function metal. The n-type work function metal includes tungsten (W), copper (Cu), titanium (Ti), silver (Ag), aluminum (Al), titanium aluminum alloy (TiAl), titanium alumina nitride (TiAlN), tantalum carbide (TaC), tantalum carbon nitride (TaCN), tantalum silicon nitride (TaSiN), manganese (Mn), or zirconium (Zr). The p-type work function metal includes titanium nitride (TiN), tungsten nitride (WN), tantalum nitride (TaN), or ruthenium (Ru). The metal gate is formed by a physical vapor deposition (PVD) process, a chemical vapor deposition (CVD) process, a plating process, an electroless plating process or another applicable process.

On the left side of the ILD structure 320, the first transistor 300 a is constructed by the gate dielectric layer 106, the gate electrode 110, and a source/drain (not shown). On the right side of the ILD structure 320, the second transistor 300 b is constructed by the gate dielectric layer 106, the gate electrode 110, and another source/drain (not shown). The first transistor 300 a and the second transistor 300 b are on opposite sidewalls of the ILD structure 320. In some embodiments, the first transistor 300 a is an n-type Metal-Oxide-Semiconductor Field-Effect-Transistor (NMOSFET), and the second transistor 300 b is a p-type Metal-Oxide-Semiconductor Field-Effect-Transistor (PMOSFET).

As shown in FIG. 3I, a sidewall of the ILD structure 320 has a bottom portion and a top portion, the gate dielectric layer 106 covers the bottom portion of the sidewall of the ILD structure 320, and the gate electrode 110 covers the top portion of the sidewall of the ILD structure 320.

In some embodiments, the ILD structure 320 has a third width W₃ in a range from about 20 nm to about 40 nm. In other words, the end-to-end critical dimension (CD) between the first transistor 300 a and the second transistor 300 b is defined by the third width W₃.

In some embodiments, an end cap distance (S₁) between the sidewall of ILD structure 320 and a sidewall of first fin structure 104 a is in a range from about 0.01 nm to about 50 nm.

It should be noted that as the size of the fin field effect transistor (FinFET) device structure 100 is decreased, controlling the end-to-end critical dimension (CD) becomes more difficult. Therefore, the disclosure uses the coating layer to control the end-to-end critical dimension (CD).

The coating layer 310 is used to reduce the width of the trench 350 from the first width W₁ to the second width W₂. By using the smaller second width W₂, a trench 354 is obtained in the polysilicon layer 304 that has a third width W₃ that is smaller than its first width W₁. Therefore, the smaller end-to-end critical dimension (CD) (such as the third width W₃ in FIG. 3H) is achieved. In addition, the profile of the polysilicon layer 304 is more vertical.

In addition, when the end-to-end critical dimension (CD) (such as the third width W₃ in FIG. 3H) is smaller, the end cap distance (S₁) becomes larger. A larger end cap distance (S₁) is beneficial for forming HK/MG stack structure.

FIGS. 4A-4F show cross-sectional representations of various stages of forming a fin field effect transistor (FinFET) device structure 100, in accordance with some embodiments of the disclosure. FIGS. 4A-4F are cross-sectional representations taken along BB′ line of FIG. 2.

Referring to FIG. 4A, the fin structure 104 and the isolation structure 108 are formed on the substrate 102. A portion of the fin structure 104 protrudes above the isolation structure 108. The dielectric layer 302 and the polysilicon layer 304 are sequentially formed on the fin structure 104 and the isolation structure 108. Afterwards, the first hard mask layer 306 a and the second hard mask layer 306 b are formed over the polysilicon layer 304.

After the second hard mask layer 306 b is formed, the photoresist layer 308 is formed on the second hard mask layer 360 b as shown in FIG. 4B, in accordance with some embodiments of the disclosure. The photoresist layer 308 is a single layer or multiple layers.

Afterwards, the photoresist layer 308 is patterned to form the trench 350 in the photoresist layer 308. One or more trenches 350 may be formed. The number of the trenches 350 may be adjusted according to the actual application. The trench 350 has a fourth width W₄. In some embodiments, the fourth width W₄ is in a range from about 40 nm to about 80 nm.

After the trench 350 is formed in the photoresist layer 308, the coating layer 310 is conformally formed in the trench 350 and on the photoresist layer 308 as shown in FIG. 4C, in accordance with some embodiments of the disclosure.

The coating layer 310 is a fluorine-containing polymer. The coating layer 310 is configured to reduce the width of the trench 350. After forming the coating layer 310, the trench 350 has a reduced fifth width W₅. Therefore, the fifth width W₅ is smaller than the fourth width W₄.

In some embodiments, the coating layer 350 is formed by a plasma process with a coating gas. The coating gas includes a fluorine-containing gas, such as tetrafluoromethane (CF₄), difluoromethane (CH₂F₂), sulfur hexafluoride (SF₆), nitrogen trifluoride (NF₃), another applicable gas, or combinations thereof.

After the coating layer 310 is formed, the photoresist layer 308, the coating layer 310, a portion of the first hard mask layer 306 a and a portion of the second hard mask layer 306 b are etched by a number of etching processes as shown in FIG. 4D, in accordance with some embodiments of the disclosure. As a result, one or more trenches 352 are formed in the first hard mask layer 306 a and the second hard mask layer 306 b. The trench 352 has a sixth width W₆ which is slightly larger than the fifth width W₅.

Afterwards, the dielectric layer 302 and the polysilicon layer 304 are patterned by using the first hard mask layer 306 a and the second hard mask layer 306 b as a mask as shown in FIG. 4E, in accordance with some embodiments of the disclosure. As a result, a trench 354 (or called an end-to-end gap) is formed in the polysilicon layer 304.

Afterwards, the first hard mask layer 306 a and the second hard mask layer 306 b are removed, and a dielectric material is filled into the trench 354 and on the polysilicon layer 304 as a mask as shown in FIG. 4F, in accordance with some embodiments of the disclosure.

After the trench 354 is filled, a portion of the excess dielectric material out of the trench 354 is removed by a planarizing process, such as a chemical mechanical polishing process (CMP). As a result, an inter-layer dielectric (ILD) structure 320 is formed.

Afterwards, the polysilicon layer 304 and the dielectric layer 302 are removed, and the gate dielectric layer 106 and the gate electrode 110 are formed on the fin structure 104 as shown in FIG. 4G, in accordance with some embodiments of the disclosure. In some embodiments, the gate dielectric layer 106 is a high dielectric constant (high-k) dielectric layer, and the gate electrode 110 is metal gate electrode. In other words, a HK/MG stack structure is formed on the fin structure 104.

As shown in FIG. 4G, the gate dielectric layer 106 and the gate electrode 110 are divided into four parts, and a first transistor 400 a, a second transistor 400 b, a third transistor 400 c and a fourth transistor 400 d are formed respectively. A first transistor 400 a is constructed by the gate dielectric layer 106 and the gate electrode 110, and a second transistor 400 b is constructed by the gate dielectric layer 106 and the gate electrode 110.

The ILD structure 320 is located between the first transistor 400 a and the second transistor 400 b. In addition, the ILD structure 320 is located between the third transistor 400 c and the fourth transistor 400 d.

In some embodiments, the sixth width (W₆) between the first transistor 400 a and the second transistor 400 b is in a range from about 10 nm to about 50 nm. In other words, the end-to-end critical dimension (CD) between two transistors is defined by the sixth width W₆.

It should be noted that the patterned photoresist layer 308 has a trench 350 with a fourth width W₄, and the trench 350 has a reduced fifth width W₅ after forming the coating layer 310 in the trench 350. The patterned photoresist layer 308 is used to pattern the underlying first hard mask layer 306 a and the second hard mask layer 306 b. Once the trench 350 has a reduced fifth width W₅, the trench 352 formed in the first hard mask layer 306 a and the second hard mask layer 306 b also have a reduced sixth width W₆. Afterwards, the trench 354 also has a reduced sixth with W₆ compared to the original fourth width W₄ of the trench 350. Therefore, the end-to-end critical dimension (CD) (or the fifth width W₆) is controlled by adjusting the thickness of the coating layer 310. Furthermore, because the polysilicon layer 304 is selectively etched by the above mentioned etching process (such as the third etching process 15), the profile the polysilicon layer 304 is more vertical.

Embodiments for forming fin field effect transistor (FinFET) device structure are provided. A first fin structure and a second fin structure are formed on a substrate. A first transistor is formed on the first fin structure and a second transistor is formed on the second fin structure. An inter-layer dielectric (ILD) structure is formed between the first transistor and the second transistor. An end-to-end critical dimension (CD) between the first transistor and the second transistor is defined by the width of the ILD structure. The width of the ILD structure is defined by a first trench formed in the ILD structure, and the first trench is indirectly defined by a second trench in a photoresist layer which is formed on the hard mask layers and the fin structures. By forming a coating layer in the second trench, the width of the second trench is reduced, and thus the width of the ILD structure is indirectly reduced. Therefore, the end-to-end critical dimension (CD) is well controlled by adjusting the coating thickness of the coating layer.

Furthermore, because the end-to-end critical dimension is reduced, the end cap distance is large enough to form a HK/MG structure. In addition, a vertical profile of gate structure is obtained. Furthermore, before forming the coating layer, a pre-cleaning process is performed to the second trench to remove residue, and therefore a line-end bridge problem is avoided.

In some embodiments, a fin field effect transistor (FinFET) device structure is provided. The FinFET device structure includes a substrate and a first fin structure and a second fin structure extending above the substrate. The FinFET device structure also includes a first transistor formed on the first fin structure and a second transistor formed on the second fin structure. The FinFET device structure further includes an inter-layer dielectric (ILD) structure formed in an end-to-end gap between the first transistor and the second transistor, and the end-to-end gap has a width in a range from about 10 nm to about 50 nm.

In some embodiments, a fin field effect transistor (FinFET) device structure is provided. The FinFET device structure includes a substrate and an isolation structure formed on the substrate. The FinFET device structure also includes a first fin structure embedded in the isolation structure and a first transistor formed on the first fin structure. The FinFET device structure further includes a second transistor formed on the first fin structure and the isolation structure. The FinFET device structure includes an inter-layer dielectric (ILD) structure formed in an end-to-end gap between the first transistor and the second transistor, and the end-to-end gap has a width in a range from about 10 nm to about 50 nm.

In some embodiments, a method for forming a fin field effect transistor device structure is provided. The method includes providing a substrate and forming a first fin structure and a second fin structure extending above the substrate. The method also includes forming a dielectric layer on the first fin structure and the second fin structure and forming a polysilicon layer, a hard mask layer and a photoresist layer on the dielectric layer. The method also includes patterning the photoresist layer to form a first trench in the photoresist layer, and the first trench has a first width. The method includes conformally forming a coating layer in the first trench to form a second trench in the photoresist layer, and the second trench has a second width and the second width is smaller than the first width. The method further includes patterning the hard mask layer by using the photoresist layer as a mask and patterning the polysilicon layer by using the hard mask as a mask to form an end-to-end gap between the first fin structure and a second fin structure. The end-to-end gap has a third width, and the third width is smaller than the first width.

One general aspect includes a method for forming a semiconductor device structure, including: providing a substrate; forming a first fin structure and a second fin structure extending from the substrate by etching a portion of the substrate; forming a polysilicon layer and a masking layer over the first fin structure and the second fin structure; patterning the masking layer to form a first opening in the masking layer, where the first opening has a first dimension; lining the first opening to form a second opening, where the second opening has a second dimension and the second dimension is smaller than the first dimension; and patterning the polysilicon layer through the second opening to form an end-to-end gap between the first fin structure and the second fin structure.

Another general aspect includes a method for forming a semiconductor device structure, including: providing a substrate; forming a material layer and a masking layer over the substrate; patterning the masking layer to form a first opening in the masking layer, where the first opening has a first dimension; lining the first opening to form a second opening, where the second opening has a second dimension and the second dimension is smaller than the first dimension; and patterning the material layer through the second opening by using the masking layer as a mask to form a third opening in the material layer where the third opening has a third dimension, and the third dimension is smaller than the first dimension.

Yet another general aspect includes a for forming a semiconductor device structure, including: forming a first fin structure and a second fin structure extending from a substrate by etching a portion of the substrate; forming a material layer and a masking layer over the first fin structure and the second fin structure; patterning the masking layer to form a first opening where the first opening has a first width; depositing a coating layer in the first opening to form a second opening where the second opening has a second width and the second width is smaller than the first width; and applying an etchant through the second opening to pattern the material layer to form an end-to-end gap in the material layer, the end gap being between the first fin structure and a second fin structure, where the end-to-end gap has a third width, and the third width is smaller than the first width.

The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure. 

What is claimed is:
 1. A method for forming a semiconductor device, the method comprising: forming a first fin structure and a second fin structure extending from a substrate; forming a material layer and a masking layer successively over the first fin structure and the second fin structure; patterning the masking layer to form a first opening in the masking layer; reducing a width of the first opening by lining a coating layer along sidewalls and a bottom of the first opening; removing portions of the coating layer; and after removing portions of the coating layer, patterning the material layer through the first opening to form an end-to-end gap between the first fin structure and the second fin structure.
 2. The method of claim 1, wherein forming the material layer comprises forming a polysilicon layer as the material layer.
 3. The method of claim 2, wherein forming the masking layer comprises: forming at least a hard mask layer over the material layer; and forming at least a photoresist layer over the hard mask layer.
 4. The method of claim 1, wherein lining the coating layer comprises forming a conformal polymer layer along the sidewalls and the bottom of the first opening.
 5. The method of claim 4, wherein the conformal polymer layer is formed using a plasma process.
 6. The method of claim 5, wherein the plasma process is performed using a fluorine-containing gas selected from the group consisting of tetrafluoromethane (CF₄), difluoromethane (CH₂F₂), sulfur hexafluoride (SF₆), nitrogen trifluoride (NF₃), and combinations thereof.
 7. The method of claim 1, wherein the masking layer comprises a hard mask layer over the material layer and a photoresist layer over the hard mask layer, wherein removing portions of the coating layer comprises: performing a first etching process to remove the coating layer from an upper surface of the photoresist layer; and after the first etching process, performing a second etching process to remove upper portions of the photoresist layer and to recess the coating layer.
 8. The method of claim 7, wherein patterning the material layer comprises: after the second etching process, performing a third etching process to remove remaining portions of the coating layer and remaining portions of the photoresist layer, wherein the third etching process further removes portions of the hard mask layer underlying the first opening to form a patterned hard mask layer; and after the third etching process, performing a fourth etching process to pattern the material layer using the patterned hard mask layer as an etching mask.
 9. The method of claim 1, further comprising performing a pre-cleaning process to clean the first opening before lining the coating layer along the sidewalls and the bottom of the first opening.
 10. The method of claim 9, wherein performing the pre-cleaning process comprises performing a plasma cleaning process.
 11. A method for forming a semiconductor device, the method comprising: forming a first gate dielectric layer over a fin that protrudes above a substrate; forming a first gate electrode layer over the first gate dielectric layer; forming a mask layer and a photoresist layer successively over the first gate electrode layer; forming a first opening in the photoresist layer; lining sidewalls and a bottom of the first opening with a coating layer to form a second opening in the photoresist layer; removing an upper portion of the photoresist layer and an upper portion of the coating layer; etching through the second opening to pattern the mask layer; and patterning the first gate electrode layer using the patterned mask layer as a mask.
 12. The method of claim 11, wherein lining the sidewalls and the bottom of the first opening with the coating layer comprises conformally forming a polymer layer as the coating layer over the photoresist layer and in the first opening.
 13. The method of claim 11, wherein removing the upper portion of the photoresist layer and the upper portion of the coating layer comprises: performing a first etching process to remove the coating layer from an upper surface of the photoresist layer; and performing a second etching process to remove the upper portion of the photoresist layer and to reduce a height of the coating layer.
 14. The method of claim 11, wherein after etching through the second opening to pattern the mask layer, the patterned mask layer has a third opening.
 15. The method of claim 14, wherein the first opening has a first width, the second opening has a second width, and the third opening has a third width, wherein the third width is larger than the second width but smaller than the first width.
 16. The method of claim 14, wherein patterning the first gate electrode layer extends the third opening through the first gate electrode layer and through the first gate dielectric layer.
 17. A method for forming a semiconductor device, the method comprising: forming a first fin protruding above a substrate; forming a dummy gate dielectric layer over the first fin; forming a dummy gate layer over the dummy gate dielectric layer; forming a masking layer over the dummy gate layer; forming a trench in the masking layer; reducing a width of the trench by lining sidewalls and a bottom of the trench with a coating layer; after reducing the width of the trench, patterning the masking layer through the trench; and transferring a pattern of the patterned masking layer to the dummy gate layer and to the dummy gate dielectric layer.
 18. The method of claim 17, wherein the masking layer comprises a first mask layer and a second mask layer formed successively over the dummy gate layer, wherein forming the trench in the masking layer comprises forming the trench partially through the masking layer such that the trench extends through the second mask layer but not the first mask layer.
 19. The method of claim 17, wherein reducing the width of the trench comprises forming a conformal polymer layer along the sidewalls and the bottom of the trench.
 20. The method of claim 17, wherein transferring the pattern of the patterned masking layer to the dummy gate layer and to the dummy gate dielectric layer forms dummy gates and dummy gate dielectric, wherein the method further comprises replacing the dummy gates and dummy gate dielectric with metal gates and high-K gate dielectric, respectively. 